The Verdict: Clear Path
As an EU, EEA, UK or Swiss citizen you can work in Ireland without any permit. Get a PPS number and start work.
EU, EEA and Swiss citizens have free movement, and British citizens the same right under the Common Travel Area. There is no stamp, no salary threshold, no occupation list and no tie to one employer, and you can be self-employed.
A PPS number is what you need to be paid and taxed correctly, so arrange it first.
Every period of your residence counts towards naturalisation: five years in the last nine. Check first whether a parent or grandparent born on the island of Ireland makes you a citizen already.